Authorities said he was with two friends who watched him go downstream in the rapids until he was out of sight. Those people called 911.

A search of the banks Monday night and Tuesday turned up nothing.

Fish and Game officials said the water was rough, the current was strong and the water temperature was in the mid-40s.

They said divers will resume the search again Wednesday.

Authorities said conditions on New Hampshire's lakes and rivers are extremely dangerous right now, and everyone should avoid them until things improve.

Officials said they are also concerned about a social media trend called Polar Plunge, in which people jump into cold water. They said there are some indications this incident was related to the trend, though there is no evidence of a request or dare being made.